Accession Number:

ADA063064

Title:

Sinterable Powders from Laser Driven Reactions

Descriptive Note:

Status rept. 1 Jul 1977-30 Jun 1978

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE ENERGY LAB

Personal Author(s):

Report Date:

1978-10-01

Pagination or Media Count:

84.0

Abstract:

Novel methods for producing ideal powders for fabricating Si3N4 ceramic parts have been investigated. The characteristics sought were principally uniformly small diameter, equiaxed, high purity particles which are free of agglomerates. Two laser processes were studied. In the first, a CO2 laser source was used to heat the reactant gases by coupling directly to them. Silicon Si and Si3N4 powders have been synthesized directly from SiH4 and NH3 SiH4 mixtures respectively. The spatially well-defined reaction zone and the combination of the rapid heating rates with the short times at reaction temperatures yielded very uniform and small diameter particles. Si3N4 powders were produced with particle diameters entirely within the range of 100-200 A. The particles are equiaxed and nearly spherical. The Si powders had the same general characteristics, but exhibited a slightly larger range of diameters. The second process uses selective heating to reduce the size of oversized particles or agglomerates as well as modifying the shape of high aspect ratio particles. This process is based on the decreasing absorption efficiency of a particle to light when its diameter is less than the wavelength of the incident light. Light induced comminution was demonstrated. We have successfully demonstrated both processes for producing superior Si and Si3N4 powders.

Subject Categories:

  • Lasers and Masers
  • Ceramics, Refractories and Glass
  • Manufacturing and Industrial Engineering and Control of Production Systems

Distribution Statement:

APPROVED FOR PUBLIC RELEASE